It is possible that the best HIV vaccine protection will be achieved by inducing a viral specific response at both the mucosal and systemic levels. Immunization with SIV mac239 Env DNA elicits a systemic immune response with both viral specific neutralizing antibodies and CTLs. The overall goal of this project is to develop conditions that maximize the systemic immune response and elicit a viral specific immune response at the mucosal level following immunization with SIVmac239 Env DNA. Specifically, the aim of this proposal is to test the potential of improving systemic and mucosal immunity by removing the stratum corneum barrier before vaccinating with SIVmac239 Env DNA on mouse skin. The stratum corneum skin layer is the main barrier to skin penetration. By removing this barrier layer, the DNA vaccine will be taken-up by the cells of the dermis that have enhanced access to the lymphatic channels found in the dermis layer. This will increase the trafficking of antigen expressing cells to the regional lymph nodes via the lymphatics. To accomplish this aim, the surface of the epidermal layer of skin will be removed by cellophane adhesive tape stripping before immunization. The mice will be immunized with SIVmac239 Env DNA by either intradermal inoculation with the gene gun or by painting the vaccine topically onto the skin. Virus-specific antibodies in the serum and saliva will be measured by ELISA and in a neutralization assay. A standard chromium release cytotoxicity assay will be employed to determine the presence of the cellular response.